I. Lima

Acromegaly Has a Negative Influence on Trabecular Bone, But Not on Cortical Bone, as Assessed by High-Resolution Peripheral Quantitative Computed Tomography

INTRODUCTION Acromegaly is one of the causes of secondary osteoporosis, although studies of bone mineral density (BMD) have yielded conflicting results and none of them have evaluated the bone properties. OBJECTIVES AND PATIENTS Our objective was to correlate, in a cohort of 82 acromegalic patients, BMD and bone microarchitecture, using dual-energy x-ray absorptiometry and high-resolution peripheral quantitative computed tomography, with the presence of type 2 diabetes mellitus (T2DM), disease activity, and gonadal status and to compare these bone parameters between 45 eugonadal acromegalic patients and 45 healthy controls. RESULTS Acromegalic patients with T2DM had lower trabecular density and trabecular bone volume to tissue volume ratio in the distal tibia. Patients with active acromegaly exhibited a higher BMD and T-score in the lumbar spine (P = .02 for both) and a higher cortical density in the distal tibia when compared with those with controlled acromegaly (P = .001). After multiple linear regression (including age, presence of T2DM, acromegaly activity, and gonadal status), eugonadism remained the main determinant of bone parameters. The 45 acromegalic patients with eugonadism were compared with 45 age- and sex-matched controls and exhibited lower trabecular densities and impaired microstructures. CONCLUSIONS Acromegaly appears to have a deleterious effect on trabecular bone microarchitecture, and in this specific population, the gonadal status might be more important than T2DM or acromegaly activity in determining bone health. High-resolution peripheral quantitative computed tomography seems promising for evaluating acromegalic bone properties and for addressing the limitations posed by dual-energy x-ray absorptiometry.

Is trabecular bone related to primary stability of miniscrews

OBJECTIVE To compare the primary stability of miniscrews inserted into bone blocks of different bone mineral densities (BMDs) with and without cortical bone, and investigate whether some trabecular properties could influence primary stability. MATERIALS AND METHODS Fifty-two bone blocks were extracted from fresh bovine pelvic bone. Four groups were created based on bone type (iliac or pubic region) and presence or absence of cortical bone. Specimens were micro-computed tomography imaged to evaluate trabecular thickness, trabecular number, trabecular separation, bone volume density (BV/TV), BMD, and cortical thickness. Miniscrews 1.4 mm in diameter and 6 mm long were inserted into the bone blocks, and primary stability was evaluated by insertion torque (IT), mini-implant mobility (PTV), and pull-out strength (PS). RESULTS Intergroup comparison showed lower levels of primary stability when the BMD of trabecular bone was lower and in the absence of cortical bone (P≤.05). The Pearson correlation test showed correlation between trabecular number, trabecular thickness, BV/TV, trabecular BMD, total BMD, and IT, PTV, and PS. There was correlation between cortical thickness and IT and PS (P≤.05). CONCLUSION Cancellous bone plays an important role in primary stability of mini-implants in the presence or absence of cortical bone.

Lean mass as a predictor of bone density and microarchitecture in adult obese individuals with metabolic syndrome

The effects of obesity and metabolic syndrome (MS) on bone health are controversial. Furthermore, the relationship between body composition and bone quality has not yet been determined in this context. The aim of this study was to investigate the correlations between body composition and bone mineral density (BMD) and bone microstructure in obese individuals with MS. This cross-sectional study assessed 50 obese individuals with MS with respect to their body composition and BMD, both assessed using dual X-ray absorptiometry, and bone microarchitecture, assessed by high-resolution peripheral quantitative computed tomography (HR-pQCT) of the distal tibia and radius. Several HR-pQCT measurements exhibited statistically significant correlations with lean mass. Lean mass was positively correlated with parameters of better bone quality (r: 0.316-0.470) and negatively correlated with parameters of greater bone fragility (r: -0.460 to -0.310). Positive correlations were also observed between lean mass and BMD of the total femur and radius 33%. Fat mass was not significantly correlated with BMD or any HR-pQCT measurements. Our data suggest that lean mass might be a predictor of bone health in obese individuals with MS.

Brain shape convergence in the adaptive radiation of New World monkeys

Significance The evolutionary diversification of brain morphology is one of the most prominent features of the primate adaptive radiation and a likely determinant of primate evolutionary success. However, the ecological factors responsible for the diversification of the primate brain are largely unknown. In this work, we use a comparative approach to study brain diversification during the adaptive radiation of a major primate clade—the New World monkeys. We show that brain morphology evolved in association with the occupation of several ecological niches, and that convergence in brain morphology among clades may be associated with an evolutionary increase in the complexity of social behaviors. Primates constitute one of the most diverse mammalian clades, and a notable feature of their diversification is the evolution of brain morphology. However, the evolutionary processes and ecological factors behind these changes are largely unknown. In this work, we investigate brain shape diversification of New World monkeys during their adaptive radiation in relation to different ecological dimensions. Our results reveal that brain diversification in this clade can be explained by invoking a model of adaptive peak shifts to unique and shared optima, defined by a multidimensional ecological niche hypothesis. Particularly, we show that the evolution of convergent brain phenotypes may be related to ecological factors associated with group size (e.g., social complexity). Together, our results highlight the complexity of brain evolution and the ecological significance of brain shape changes during the evolutionary diversification of a primate clade.

X-ray microtomography application in pore space reservoir rock.

Characterization of porosity in carbonate rocks is important in the oil and gas industry since a major hydrocarbons field is formed by this lithology and they have a complex media porous. In this context, this research presents a study of the pore space in limestones rocks by x-ray microtomography. Total porosity, type of porosity and pore size distribution were evaluated from 3D high resolution images. Results show that carbonate rocks has a complex pore space system with different pores types at the same facies.

Encephalization and diversification of the cranial base in platyrrhine primates.

The cranial base, composed of the midline and lateral basicranium, is a structurally important region of the skull associated with several key traits, which has been extensively studied in anthropology and primatology. In particular, most studies have focused on the association between midline cranial base flexion and relative brain size, or encephalization. However, variation in lateral basicranial morphology has been studied less thoroughly. Platyrrhines are a group of primates that experienced a major evolutionary radiation accompanied by extensive morphological diversification in Central and South America over a large temporal scale. Previous studies have also suggested that they underwent several evolutionarily independent processes of encephalization. Given these characteristics, platyrrhines present an excellent opportunity to study, on a large phylogenetic scale, the morphological correlates of primate diversification in brain size. In this study we explore the pattern of variation in basicranial morphology and its relationship with phylogenetic branching and with encephalization in platyrrhines. We quantify variation in the 3D shape of the midline and lateral basicranium and endocranial volumes in a large sample of platyrrhine species, employing high-resolution CT-scans and geometric morphometric techniques. We investigate the relationship between basicranial shape and encephalization using phylogenetic regression methods and calculate a measure of phylogenetic signal in the datasets. The results showed that phylogenetic structure is the most important dimension for understanding platyrrhine cranial base diversification; only Aotus species do not show concordance with our molecular phylogeny. Encephalization was only correlated with midline basicranial flexion, and species that exhibit convergence in their relative brain size do not display convergence in lateral basicranial shape. The evolution of basicranial variation in primates is probably more complex than previously believed, and understanding it will require further studies exploring the complex interactions between encephalization, brain shape, cranial base morphology, and ecological dimensions acting along the species divergence process.

Bone density and microarchitecture in endogenous hypercortisolism

Osteoporosis is a serious and underestimated complication of endogenous hypercortisolism that results in an increased risk of fractures, even in patients with normal or slightly decreased bone mineral density (BMD). Alterations in bone microarchitecture, a very important component of bone quality, may explain bone fragility. The aim of this study was to investigate bone density and microarchitecture in a cohort of patients with endogenous Cushings syndrome (CS).

Short-term in vivo evaluation of zinc-containing calcium phosphate using a normalized procedure

The effect of zinc-substituted calcium phosphate (CaP) on bone osteogenesis was evaluated using an in vivo normalized ISO 10993-6 protocol. Zinc-containing hydroxyapatite (ZnHA) powder with 0.3% by wt zinc (experimental group) and stoichiometric hydroxyapatite (control group) were shaped into cylindrical implants (2×6 mm) and were sintered at 1000 °C. Thermal treatment transformed the ZnHA cylinder into a biphasic implant that was composed of Zn-substituted HA and Zn-substituted β-tricalcium phosphate (ZnHA/βZnTCP); the hydroxyapatite cylinder was a highly crystalline and poorly soluble HA implant. In vivo tests were performed in New Zealand White rabbits by implanting two cylinders of ZnHA/βZnTCP in the left tibia and two cylinders of HA in the right tibia for 7, 14 and 28 days. Incorporation of 0.3% by wt zinc into CaP increased the rate of Zn release to the biological medium. Microfluorescence analyses (μXRF-SR) using synchrotron radiation suggested that some of the Zn released from the biomaterial was incorporated into new bone near the implanted region. In contrast with previous studies, histomorphometric analysis did not show significant differences between the newly formed bone around ZnHA/βZnTCP and HA due to the dissolution profile of Zn-doped CaP. Despite the great potential of Zn-containing CaP matrices for future use in bone regeneration, additional in vivo studies must be conducted to explain the mobility of zinc at the CaP surface and its interactions with a biological medium.

Methodology for attainment of density and effective atomic number through dual energy technique using microtomographic images

Dual energy technique for computerized microtomography shows itself as a promising method for identification of mineralogy on geological samples of heterogeneous composition. It can also assist with differentiating very similar objects regarding the attenuation coefficient, which are usually not separable during image processing and analysis of microtomographic data. Therefore, the development of a feasible and applicable methodology of dual energy in the analysis of microtomographic images was sought.

Influence of bone architecture on the primary stability of different mini-implant designs.

INTRODUCTION Mechanical interlocking between a mini-implant (MI) and the bone substrate reflects directly on the primary stability achieved. The purposes of this study were to evaluate MI design performance in distinct bone substrates and correlate geometric characteristics with insertion site quality. METHODS Two types of self-drilling MIs (1.6 × 8 mm) were allocated to 2 groups according to their geometric designs: Tomas system (Dentaurum, Ispringen, Germany) and Dual-Top (Rocky Mountain Orthodontics, Denver, Colo). Forty sections (8 × 10 mm) were taken from bovine pelvic ilium and pubic bone. Geometric design characteristics were evaluated using scanning electron microscope imaging and Image-Pro Insight software (Media Cybernetics, Rockville, Md). Bone quality parameters were assessed with a microcomputed tomography system, and primary stability was evaluated by insertion torque and pull-out strength. Intergroup comparisons were performed with analysis of variance and Tukey tests, and the Pearson correlation test was carried out (P <0.05). RESULTS No significant difference was observed in the comparisons of the groups (Tomas: insertion torque, 12.87 N·cm; pull-out strength, 181 N; and Dual-Top: insertion torque, 9.95 N·cm; pull-out strength, 172.5 N) in the ilium. However, the Tomas group had a marked increase in insertion torque (25.08 N·cm; P <0.05) in the pubic bone. CONCLUSIONS MI mechanical performance differed according to bone quality parameters, indicating that certain geometric parameters may be set depending on the insertion substrate.